Although I doubt this is the sole factor behind the growing concentration of wealth, it is a factor I’ve been thinking about – and that I’m keen to see someone else quantify.

One thing we have to keep in mind is that standard economic theory does predict a growing concentration of wealth as

the idea of “rational expectations” when some agents are not rational implies that rational agents will tend to suck up wealth from irrational agents – it is a common misconception that “rational expectations” requires any agents to be “rational” in the strictest sense … however, it does imply that agents that are “more rational” do receive transfers through time from their “irrational” buddies.

the fact that individuals have different discount factors suggests that more patient individuals who are more patient will tend to accumulate more wealth.

Now this isn’t necessarily even an issue, after all if people built up wealth due to their own choices they deserve it. However, trying to understand how much of the recent change is due to the full functioning of financial markets in recent decades, how much is due to demographics, and how much is due to other policy change is important to understand before we really know anything.